Conversion of hydrocarbons



Dec. 4, 1945. e. B. ZIMMERMAN CONVERSION OF HYDROCARBONS 7 Filed Feb. 11, 1942 2 Sheets-Sheet 1 DEI-LYPIgOGEN- E-JJAI IRDIFTNOE I N a A A l N s 1 ZONE. ZONE f I DEBUTANl' DEISOBUTAN- ALKYLAT|QN ZATION IZATION 1 20m: ZONE Q FIGURE 1 1 30 DEHYDROGEN- BUTADIENE' ATION '6 SEPARATION (4 w ZONE ZONE 3| 4o 34\ K F 2| DEBUTANI- DEISOBUTAN- K AT 5 PAR T| ZATION '7 IZATION AL JS E 3 ON ZONE ZONE FIGURE 2 'INVENTOR GORDON B.ZIMMERMAN.

/ ATTORNEY Dec. 4, 1945.

Filed Feb. 11, 1942 DEHYDROGENATION ZONE SEPARATION ZONE FIGURE 3 2. Shegts-Sheet 2 BUTADIENE SEPARATION ZONE INVENTOR GORDON B. ZIMMERMAN 1 ATTORNEY Patented Dec. 4, 1945 CONVERSION OF HYDBOCARBONS Gordon B. Zimmerman, Chicago, 111., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application February 11, 1942, Serial No. 430,511

15 Claims.

This invention relates to a combination'process for the production or butadiene and alkylate gasoline. Butadiene is used as one of the raw materials in the preparation of synthetic rubber and its production at the present time is of extreme importance. Alkylate gasoline is used in the preparation of aviation gasoline and its production is likewise of extreme importance at the present time.

More specifically, the invention comprises a series of inter-dependent and cooperative steps involving the dehydrogenation of normal butane and/or normal butylene into butadiene, and the alkylation of isobutane with butylenes.

In one embodiment of the invention, the charging stock to the process may comprise normal butane, alone or in admixture with isobutane. quantities from natural g s or gasoline, straight run gas or gasoline, or from other available sources. In another embodiment of the invention the charging stock may comprise mixtures 01 butanes and butylenes, which mixtures are available in large quantities from the gases produced incidentally to the cracking oi heavy hydrocarbon oils for the production of gasoline. The charging stock may'include various percentages of materials boiling below and above the C4 hydrocarbons but, in its preferred operation, the quantity of such higher and lower boiling materials is kept to a minimum.

Normal butane is usually recovered in admixture with isobutane and one voi the difliculties accompanying the production of butadiene is due to the presence of the isobutane from the charge as well as the iso compounds produced incidentally during the dehydrogenation reaction. Likewise, butylenes are usually recovered commercially in admixture with normal butane and one of the difliculties in the alkylation of isobutane by the butylenes is due to the presence or the normal butane. The present invention proposes a process whereby the above difliculties may be eliminated or greatly minimized and whereby maximum utilization of the normal compounds for the production of butadiene is accomplished. I

The exact operation of the process will depend, to a large extent, upon the composition or the charging stock, and several of the various modiflcations of the invention will be described in detail in the following specification.

In one specific embodiment, and particularlyin cases where the charging stock contains a large percentage of normal Ci hydrocarbons, the

These butanes are obtainable in large invention comprises dehydrogenating normal C4 hydrocarbons into butadiene, separating butadiene from the reaction products, subjecting the remaining reaction products to alkylation, either in the presence or absence of added isobutane and/or gaseous oleflns, whereby to alkylate the isobutane with the oleflns, separating isobutane from the alkylation reaction products, recycling the separated isobutane to the alkylation step, separating the remaining normally gaseous hydrocarbons comprising principally normal, butane from the normally liquid alkylation products, and supplying said separated normally gaseous hydrocarbons to the dehydrogenation step.

In another embodiment, and particularly in cases where the charging stock contains a large percentage of iso compounds, the invention comprises treating the charging stock to separate a fraction containing principally normal butane and normal butylene-2, and a fraction containing principally i-butane, i-butylene, and nvbutylene-l, dehydrogenating the first mentioned fraction into butadiene, separating butadiene fromthe reaction products of said dehydrogenation, recycling a portion of the remaining reaction products to the dehydrogenation step, commingling an additional portion of said re-' maining reaction products with the previously separated fraction containing principally l'-butane, i-butylene, and n-butylene-l, subjecting the commingled hydrocarbons to alkylation conditions whereby to alkylate the isobutane contained therein with the oleflns, separating isobutane from the alkylation reaction products, recycling the separated isobutane to said alkylation, separating and recovering normally liquid alkylation products from the residual normally gaseous products, and supplying said residual normally gaseous products to the dehydrogenation step.

The invention will be described in detail in the following specification and illustrated in the accompanying drawings, comprising Figures 1, 2

. and 3, which show several modifications oi the invention, although not with the intention of unduly limiting the same.

As used in the specification and claims, the term normal compound means straight chain hydrocarbons. The term isocompound refers to a charging stock is introduced to the process through line I and is directed into dehydrogenation zone 2. Dehydrogenation zone 2 may comprise any suitable apparatus or process of either the catalytic or non-catalytic type and may comprise either single or multiple stage operation, whereby the normal butane and/or normal butylene may be converted into butadiene. This step of the process is well known in the present state of the art and, since no invention is claimed herein for the particular apparatus or process employed, there appears no need for a detailed recitation thereof. While non-catalytic dehydrogenation may be employed, but not necessarily with equivalent results, it is usually preferred to employ catalysts. Any suitable cat-.- alyst may be so employed, satisfactory catalysts being alumina-containing orsiliceous materials composited with a compound and particularly an oxide of the elements in the left hand columns of groups IV, V, and VI of the periodic table. Temperatures usually employed are within the broad range of 900 F. to 1300 F. Either subatmospheric, atmospheric or superatmospheric pressures may be employed and, when utilizing catalysts, the pressure is generally within the range of $40 to 2 atmospheres or more.

The products from dehydrogenation zone 2 are directed therefrom through line 3 into butadiene separation zone 6. Zone 4 maylikewise comprise any suitable apparatus or system whereby the desired separation of the products introduced thereto may be accomplished, and prejerably includes suitable fractionating, distilling, and/or absorbing and stripping columns whereby the flxed gases may be separated and removed either before or after the butadiene separation. Usually it is preferable to remove the fixed gases prior to the butadiene separation. The butadiene separation may be accomplished, for example, by azeotropic distillation in the presence of ammonia. Anothe satisfactory process may comprise the use of an aqueous solution of a euprous salt. Whichever process is utilized in zone 4, the products introduced thereto are separated into lighter or fixed gases, butadiene, and remaining C4 hydrocarbons. The lighter gases, consisting primarily of hydrogen, are removed from zone 4 through line 5 to storage or elsewhere as desired. The separated butadiene is removed from zone 4 through line 6 and may be directed to storage or elsewhere as desired. The remaining C4 hydrocarbons are removed from zone 4 through line I and, although a portion thereof may be removed from the process, by well known means not illustrated, preferably at least a portion thereof is directed through lines 8 and 9 into alkylation zone i 0.

Isobutane and/or gaseous oleflns are introduced to the process through line H and are directed through line 9 into alkylation zone i0. It-

apparatus or system employed, there appears no.

need fo a detailed recitation thereof. Suitable catalysts includesulfuric acid. hydrogen fluoride, alone or together with boron fluoride, aluminum chloride, etc. These catalysts may be used alone or in conjunction with a supporting or packing material. The conditions of operation will depend upon the particular catalyst employed and upon the composition of the charge introduced to this step of the process. In general, the temperature may be within the broad range of 50 F. to 300 F. The pressure employed may be subatmospheric, atmospheric or superatmospheric.

The products from alkylation zone III are removed therefrom and are directed through line l2 into deisobutanization zone l3. Zone l3 usually will comprise one or a plurality of fractionating, distilling and/or absorbing and stripping zones whereby isobutane may be separated from the other products. The separated isobutane is removed from zone I 3 through line 8, and at least a portion thereof is recycled by way of line 9 to alkylatlon zone I0 for further use within the process. a

The remaining products, which consist of the normally liquid alkylate and the residual gases, are directed from zone ll through line I! into debutanization zone l5. Likewise, zone It may comprise any suitable apparatus in order to effect the desired separation of the normally gaseous hydrocarbons from the aikylate gasoline. The alkylate gasoline is withdrawn from zone 13 through line I8 to storage or elsewhere as desired. The gases separated from the alkylate in zone IE will comprise principally normal butane, and these gases are withdrawn through line I! and at least a portion thereof are directed I through line I into dehydrogenation zone 2 for stock contains a high percentage of isocomis essential to maintain an excess of isoparaflin in the alkylation step and the quantity of isoparaflln introduced through line II will depend upon the proportions of isobutane and olefins present in the mixture withdrawn from zone 1 which, in turn, will depend in part upon the proportion of isobutane present in the charging stock introduced through line I.

In any event, the charge introduced to zone ill will be controlled to give the desired proportion of isoparaflin to oleflns whereby to accomplish the desired alkylation. Zone in may comprise any suitable apparatus or system and, since no novelty is claimed herein for the particular pounds. Referring to Fi ure 2, all or a portion of the charging stock may be introduced to the process through line 2| into separation zone 22. The purpose of zone 22 is to separate, as far as it is practical, the isocompounds from the normal compounds. It is, of course,- preferred to separate all of the isocompounds from the normal compounds, but, due to the closeness in boiling points of isobutylene and normal butylene-l, it probably will be commercially impractical to attempt their separation. It is therefore within the scope of the invention to control the operation of zone 22 so as to separate the C4 hydrocarbons into two fractions, the first fraction comtaining the isobutane, the isobutylene and the normal butylene-l, which fraction will have a boiling range below about 25 F., andthe second fraction containing the normal butane and the normal butylene-2, which fraction will have a boiling range of above 25 F.

Zone 22 may comprise any suitable apparatus and process for effecting the desired separation. Any light gases present may be removed from zone 22 through line 23. Any products boiling above the C4 hydrocarbons may be withdrawn from zone 22 through line 24. The fraction containing the normal butane and normal butylenespond to that heretofore set forth in connection with zone 2. Dehydrogenation products are withdrawn from zone 28 through line 21 and are directed into butadiene separation zone 28. Zone 23 will likewise correspond to zone 4 and the description heretofore set forth in connection with zone 4 will apply to zone 28. Butadicne is removed from zone 23 through line 29 and the fixed gases may be removed from zone 28 through line 33. The remaining reaction products are removed from zone 23 through line 3|, and the fulrther treatment thereof may be varied somew at.

All or a portion of the reaction products withdrawn through line 3| may be recycled by way of lines 32, 33 and 23 to dehydrogenation zone 26 for further conversion therein, or all'or a portion of these reaction products may be directed by way of lines 3|, 34 and 2| to separation zone 22 for further treatment therein as previously set forth, or all or a portion of these reaction products may be directed by way of lines 3! and 33 to alkylation zone 38. Since approximately 2 to 4 mol per cent of normal compounds are converted into isocompounds in dehydrogenation zone 28, at least a portion'of the isocompounds produced must be removed from the products being recycled to zone 28, in order to avoid these compounds building up within the process and/ or their conversion to undesired products. Experiments have demonstrated that the isocompounds will more readily form carbon and hydrogen during the dehydrogenation reaction, and the presence of the isocompounds will not only-increase the required size and capacity of zone 26, but will also increase the amount of carbon which will have to be removed from the catalyst by oxidation and, accordingly, increase the size of the regenerating equipment required to accomplish this oxidation. In general, theamount of said reaction products recycled to zone 28 will comprise between about 50 to about 90 per cent of these hydrocarbons, while the remaining 10 to 50 per cent will be diverted either through line 34 or line 33, although in certain instances, it may be desired to recycle or divert greater or less proportions of these hydrocarbons.

The other fraction, comprisin the isobutane, isobutylene and normal butylene-l, is withdrawn from separation zone 22 through line 31 and is introduced into alkylation zone 36. Alkylation zone 36 is similar to alkylation zone Ill and the description heretofore set forth in connection with zone III will apply to zone 35. The products from zone 38 are directed through line 33 separation zone is disposed after the dehydrogenation zone and prior to the butadiene separation zone. This permits separation of the fixed gases, normal butane, and normal butylene-2 from the dehydrogenation reaction products prior to the separation of the butadicne'. In this erabodiment of the invention, the remaining C4 hydrocarbons, after separation from the butadiene, will comprise principally isobutane, isobutylene, and normal butylene-Land this fraction may conveniently be supplied direct to the alkylation zone. Figure 3 of the drawings illustrates only the modifications to Figure 2 in order to describe the differences therefrom. Like parts have been indicated by like numbers. Referring to Figure 3, the normal butane-containing fraction is directed through line 25 into dehydrogenation. zone 26. separation zone 50. Separation zone Ell may comprise any suitable apparatus to accomplish the desired separation and this zone may comprise, for example, one or a plurality of fractionation, distilling, and/or absorbing and stripping columns. Fixed gasesare removed through line ill. The higher boiling fraction, which comprises the normal butane and normal butylene-Z is withdrawn from zone through line 53 and may be recycled, all or in part, to' dehydrogenation zone 26. n

The remaining C4 hydrocarbons, which comprise the isobutane, isobutylene, normal butylone-l and butadiene, are removed from zone 50 through line 52 .and are directedginto butadiene separation zone 28, from which the butadiene is removed through line 29 and the other C4 hydrocarbons are removed through line it. Since these other C4 hydrocarbons comprise principally isobutane, isobutylene, and normal butylene-l, they may conveniently be supplied direct to alkylation zone 36. In this embodiment of the invention, separation zone 22 may be eliminated if desired.

The following example is introduced for the purpose of illustrating one specific operation of y the invention, although not with the intention of unduly limiting the same.

The charging stock comprises a butane-butylene fraction, recovered as the overhead product from the stabilization of cracked gasoline. Since this charge contains isocompounds, the preferred operation is similar to that illustrated in Figure 2 of the drawings. The charge is separated into a fraction containing the isobutane, isobutylene and normal butylene-l, and a fraction containintodeisobutanization zone 39. Zone 39 will likewise correspond to deisobutanization zone l3. The separated isobutane is recycled by way of lines 40 and 35 to zone 36. The alkylate and remaining C4 hydrocarbons are withdrawn from zone 39 and are directed through line 4| into debutanization zone 42, which corresponds in trated in Figure 3, which is a modification of theflow shown in Figure 2. In this modification a ing the normal butane and normal butylene-2. The latter fraction may be dehydrogenated in the presence of an alumina-chromia catalyst at a temperature of about 1200 F. and under a subatmospheric pressure of about mm. The products therefrom contain approximately 18 per cent by weight of 'butadiene, approximately 40 per' cent by weight of butylenes, approximately 20 per cent by weight of butanes, the remaining products being hydrogen, lighter gases and loss. The butadiene may be separated from the other products by azeotropic distillation in the presence of ammonia, and the remaining C4 hydrocarbons are split into two streams. One stream, comprising approximately 66 per cent of these C4 hydrocarbons, is recycled to the dehydrogenation zone, while the other. stream, comprising the remaining hydrocarbons, is directed to separation zone 22.

The other fraction separated in zone 22, comprising isobutane, isobutylene and normal butyl- The products therefrom are directed into ene-l, is subjected to alkylation at a temperature of about 50 F. and under a pressure of about 90 pounds per square inch in the presence of a sulfuric acid catalyst. Isobutane is separated from the alkylation products and is recycled to the alkylation zone. Alkylate gasoline is separated from the remaining C4 hydrocarbons, the former being withdrawn from the process and the latter being recycled to the dehydrogenation zone.

I claim as my invention:

1. A hydrocarbon conversion process which comprises subjecting a fraction comprising normal and isobutane to dehydrogenation to form butadiene, separating the products therefrom into hydrogen and light gases, butadiene, and

' remaining 04 hydrocarbons containing isobutane,

normal butane, and butenes, subjecting said remaining 04 hydrocarbons to alkylation to react the isobutane with the butenes, separating normal butane from the alkylation products, and. supplying the separated normal butane to said dehydrogenation step.

2. A process such as defined in claim 1 wherein isobutane is separated from the products of said alkylation step and the separated isobutane is recycled to said alkylation step.

in approximately 50 to 90 per cent 01' said remaining C4 hydrocarbons are recycled to said dehydrogenation and the remaining to 50 per cent of the residual C4 hydrocarbons are supplied to the first mentioned separation step;

10. A process such as defined in claim 8 wherein fixed gases are separated from said dehydro-.

genation products, the remaining dehydrogenation products are separated into a first fraction comprising principally n-butane and n-butylene-2 and a second fraction comprising principally isobutane, isobutylene, n-butylene-l and butadiene; said first-named fraction is recycled to the dehydrogenation step, butadiene is separated from said second-named fraction, and the remaining 04 hydrocarbons from said secondnamed fraction are supplied to said alkylation step,

11. The process of claim 6 wherein fixed gases are separated from said dehydrogenation products, the remaining dehydrogenation products 3. A hydrocarbon conversion process which comprises subjecting a mixture containing isobutane, normal butane, and olefins to alkylation whereby to alkylate the isobutane by the olefins, separating normal butane from the products of said alkylation, dehydrogenating the separated normal butane to butadiene, relatively small amounts of iso C4 hydrocarbons also being formed in the dehydrogenation step incidental to the formation of said butadiene, separating from the dehydrogenation products butadiene and a fraction containing normal butane, isobutane,

normal butylene and isobutylene, and supplying at least a portion of the last mentioned fraction to said alkyiation step,

4. A process such as defined in claim 3 wherein isobutane is separated from the products of i said alkylation step and wherein at least a portion of the separated isobutane is said alkylation step,

5. A process such as defined in claim 8 wherein said olefins comprise normal butylene.

6. A hydrocarbon conversion process which comprises separating amixture containing isobutane, normal butane, isobutylene, normal butylene-l and normal butylene-2 into, two frac-- tions, the first fraction containing the normal butane and normal butylene-2 and the second fraction containing the isobutane, isobutylene and normal butylene-l, subjecting said first fraction to dehydrogenation to convert the same into butadiene, separating the products of dehydrogenation into hydrogen and light gases, butadiene, and remaining C4 hydrocarbons, supplying at least a portion or said remaining C4 hydrocarbons and all of said previously mentioned second fraction to an alkylation step, separating normally liquid hydrocarbons from the alkylation reaction products, and supplying the residual hydrocarbons to the dehydrogenation s ep.

7. A process such as defined in claim 6 wherein at least a portion of said remaining C4 hydrocarbons is recycled to the dehydrogenation step.

8. A process such as defined in claim 6 wherein at. least a portion of said remaining C4-hydrorecycled to carbons is supplied to the first mentioned sepaare fractionated into a higher boiling fraction comprising principally n-butane and n-butylene-2 and a lower boiling traction, said higher boiling fraction is recycled to the dehydrogenation step, butadiene is recovered from said lower boiling traction, at least a portion or. the remaining C4 hydrocarbons in said lower boiling traction and all 01' said previously mentioned second fraction are supplied to an alkylation step,

normally liquid hydrocarbons are separated fromthe alkylation reaction products, and theresidual hydrocarbons in the alleviation reaction products are supplied to said dehydrogenation step.

12. A hydrocarbon conversion process which comprises subjecting a C4 fraction containing normal C4 hydrocarbon and a minor proportion 01' iso C4 hydrocarbons to the action of a dehydrogenating catalyst to form butadiene, separating from the resultant products butadiene and C4 hydrocarbons of higher molecular weight than butadiene including isobutane, normal butane,

and olefins, subjecting at least a portion of said higher molecular weight C4 hydrocarbons to alkylation to alkylate isobutane contained therein with olefins, separating normal butane from the products of the alkylating treatment and supplying said normal butane to the dehydrogenating step.

13. The process oi claim 12 further characterized in that said higher molecular weight C4 hydrocarbons are separated into a fraction comprising normal butane and normal butylene-z and a fraction comprising isobutane, isobutylene and normal butylene-l, the latter is supplied to the alkylating step and the fraction containing normal butane and normal butylene-2 is supplied to the dehydrogenating step.

14. A hydrocarbon conversion process which comprises separating a mixture containing isobutane, normal butane, isobutylene, normal butylene-l and normal butylene-2 into two frac-' tions, the first fraction containing the normal bunormal butylene-l, subjecting said first fraction tane and normal butylene-2 and the second fraction containing the isobutane, isobutylene and to dehydrogenation to convert the same into butadiene, separating the products of dehydrogenation into hydrogen and light gases, butadiene, and remaining C4 hydrocarbons, subjecting at least a portion of said remaining C4 hydrocarbons and at least a portion or the second mentioned fraction to alkylation to alkylate the isobutane with the buteues, separating normally liquid bydrocarbons from the alkylation products, and supplying the residual hydrocarbons to the dehydrogenation step.

15. The process of claim 6 wherein fixed gases are separated from said dehydrogenation products, the remaining dehydrogenation products are fractionated into a higher boiling fraction comprising principally n-butane and n-butylene- 2 and a lower boiling fraction, said higher boiling fraction is recycled to the dehydrogenation step, butadiene is recovered from said lower boiling fraction, at least a portion of the remaining C4 hydrocarbons in said lower boiling fraction and all of said previously mentioned second fraction are supplied to an alkylation step, and normally liquid hydrocarbons are separated from the alkylation reaction products.

GORDON B. ZIMIMERMAN. 

